- The Underbase is a font of knowledge in the Marvel Comics portion of the Generation One continuity family.
Within each Transformer is a database, storage of that Transformer's accumulated knowledge. The Underbase is a "collection of knowledge that underlies all databases," or rather the combined knowledge of the Transformer race. It is curated by Boltax within his Temple of Knowledge, and it is considered off-limits to either Autobot or Decepticon.
Though acquiring portions of the Underbase can be enlightening, the combined power of its knowledge could detonate a star on impact, and its mere proximity can leave a planet scorched of life. Its energies are especially damaging to Transformer microchips, though enhancement by anything organic can somewhat protect the Transformer.
Marvel Comics continuity
Millions of years ago, back on Cybertron, the Underbase was being sought by Optimus Prime and the Triggerbots just as the Cybertronian Civil War was starting. The Underbase supposedly held all of Cybertron's knowledge, and it was heavily guarded (including molten mercury mine fields, cable jungles, and collapsing floors). Unknown to Optimus Prime, Megatron and the Triggercons were following him, intent on dispatching Optimus Prime and taking the powers of the Underbase for themselves. When the Autobots arrived at Boltax's Temple of Knowledge, the Disciples of Boltax said to Prime, "You must turn back immediately, Optimus Prime, and take your warriors with you. Pain and suffering will be yours if you stay."
Prime told his men to set camp while he went to seek the knowledge of the Underbase. Not that long after, Megatron came to the gates of Boltax as well. When Boltax's disciples gave Megatron the same message about pain and suffering, Megatron instead gave those same gifts to them, as he and his troops destroyed them with firepower.
Meanwhile, Prime met up with Boltax, who welcomed him but could not give Prime exactly what he sought, but nevertheless allowed him to bathe in the knowledge of the Underbase in a chamber just beyond where they were standing. Optimus entered, but Megatron and his troops were not far behind, and Boltax was quickly dispatched as well.
Megatron entered the chamber. Realizing the truth, Prime told Megatron that the entire mountain was Boltax, who had converted himself into a giant containment vessel to store the vast energies of the Underbase, while the robot he and Megatron had talked to was merely a puppet. He then added that he'd discovered that the knowledge contained in the Underbase was too much for any one Transformer to know, and that any attempt to input the Underbase would only lead to "madness.... and death"
Not believing him, Megatron ordered his Decepticons to fire at Prime. As Megatron started boasting about his victory, he didn't see Optimus get up and press a switch, which closed the flame vents, causing the energy inside to build up. Everyone got out just in time to see the Underbase being shot out into space. Prime lamented, "Cybertron's greatest treasure - gone all because I let pride and glory - not reason - dictate my actions. All because of me. I will live with this shame for the rest of my existence." Interestingly, this incident - in that he removed the Underbase from Decepticon hands - would be one of the cornerstones of Optimus's sterling reputation.
On present-day Earth, Ratbat, Soundwave and Starscream got hold of a record of the preceding events that was stored on the Autobot cassettes, Raindance and Grand Slam. Ratbat wanted to take the Underbase for himself, but so did Starscream, who abandoned their prisoner Buster Witwicky outside the Decepticons' base of operations in Antarctica with equipment to attract the attention of both the Autobots and Decepticons. While Starscream convinced the Decepticons to fight each other, he escaped in Scorponok's ship to search for the Underbase. The Aerialbots found Buster and the rest of the Autobots followed, but not long afterwards the Decepticons were upon them!
Meanwhile, Starscream found the Underbase and started to absorb its powers but was shot out of the way by Ratbat's Decepticon ship, piloted by an Autobot/Decepticon alliance. But Starscream wasn't dead! Now, powered by a portion of the Underbase, he lifted Scorponok's ship and threw it at Ratbat's. Starscream announced, "I go now to destroy the cities of New York, Tokyo, and Buenos Aires!" Optimus Prime, predicting the potential loss of transportation, had the Ark waiting close by.
The Autobots and Decepticons separated into three groups to send to Starscream's three target cities, but Optimus Prime and Buster stayed behind. In New York, Starscream destroyed the Aerialbots, Jetfire, Bluestreak, Brawn, Gears, Goldbug, Mirage, Hoist, Hound, Jazz, the Seacons, and Blaster. Ratbat escaped, heading to the Ark, thinking Prime was going to use the Underbase for himself. In Tokyo, Starscream killed the Throttlebots, Thundercracker, Skywarp, the Dinobots, the Predacons, and Grimlock. Scorponok also left for the Ark, thinking Prime would use the Underbase for himself. In Buenos Aires, Starscream off-lined Laserbeak, Buzzsaw, Octane, Astrotrain, Blitzwing, the Technobots, the Terrorcons, Omega Supreme, and Soundwave. And before getting a chance to destroy Fortress Maximus, he heard a radio transmission and headed for the Ark.
Back on the Ark, Hi-Q (Prime's Powermaster component) and Buster launched the rocket. The rocket deflected the Underbase and altered its course, sending it directly towards Earth. At that point, Ratbat had taken Buster and Hi-Q hostage on the Ark, but Scorponok arrived, blasted everyone and went after the Underbase himself. Prime (with Hi-Q linked to him) stopped Scorponok just as the Underbase passed by.
Starscream arrived from the planet's surface and intercepted the Underbase's path, absorbing the entire thing. He began to grow and mutate until he finally exploded, demolishing all that was the Underbase.
Optimus discovered the Underbase had been linked to the centre of Cybertron - and thus to Primus himself. With Unicron approaching and no other options available, he sent six Autobots to find the former Underbase site, hoping they could tap into the energy it had drawn on and use it as an anti-Unicron weapon.
- The Underbase was concocted as a story-based means
to get rid of older products— er, to remove older characters.